Between 1991 and 2007, Miriam Goderich was promoting Barack Obama’s writing, and in particular his biography – Dreams from My Father which was published in 1995. This book made Obama rich.
In all of her promotional literature starting in 1991, she listed him as being born in Kenya – until a few weeks before he announced his candidacy for president in April 2007.
Miriam and Barry would undoubtably have attended many book signings and cocktail parties together during that time, and Miriam would undoubtably have been introducing him to various groups of people.
It is beyond implausible that Obama did not know for 17 years that she believed he was born in Kenya.